This invention relates to a connecting structure for connecting a flexible printed circuit board to a hard printed circuit board by placing the former upon the latter and then by soldering connector terminals of these printed circuit boards together, and more particularly to such a connecting structure adapted to position the flexible printed circuit board relative to the hard printed circuit board while the printed circuit boards are connected to each other.
When a flexible printed circuit board (referred to hereinafter simply as "FPC") is placed upon and soldered to a hard printed circuit board (referred to hereinafter simply as "PCB"), connection terminals of the respective printed circuit boards to be soldered together must be properly positioned relative to each other. Such positioning has conventionally been achieved, as shown in FIG. 7 of the accompanying drawings, in a manner as follows. A supporting member 2 partially utilizing any one of casings for various devices or any one of structure components to support a PCB 1 from its rear side is provided with a pin 3. The pin 3 is inserted into through-holes 1a, 4a formed through the PCB 1 and an FPC 4, respectively, and aligned with each other so as to position these printed circuit boards 1, 4 relative to each other.
In an alternative manner of positioning, the supporting member 2 has been formed with a threaded hole, instead of providing the pin 3, so that a set screw may be inserted into the through-holes 1a, 4a of the respective printed circuit boards 1, 4 until the set screw is threaded into the threaded hole and thereby the FPC 4 has been positioned relative to the PCB 1.
In a further alternative manner of positioning, side edges of the respective printed circuit boards have been put against the pin 3 to position these two printed circuit boards relative to each other, instead of forming the PCB 1 and the FPC 4 with the through-holes.
After the PCB 1 and the FPC 4 have been relatively positioned in the manner as described above, the connector terminals of the respective printed circuit boards 1, 4 are soldered together. It should be understood that reference numeral 5 in FIG. 7 designates a soldered spot.
However, the connecting structure of well-known art selectively adopting the manners of positioning as have been described above is disadvantageously accompanied with problems depending on the adopted manners of positioning. When the relatively small-sized, band-shaped FPC 4 is formed with the positioning through-hole 4a, the FPC 4 is provided along its transversely opposite side with protrusions 4c, 4c, respectively, and these protrusions 4c, 4c must be formed with through-holes 4a, 4a as shown in FIG. 8. Consequently, when a plurality of FPCs 4 are arranged in parallel one to another, the protrusions 4c, 4c are interposed between each pair of adjacent FPCs 4. Such arrangement inevitably enlarges a space occupied by these FPCs 4 and the device equipped with these FPCs 4 should become correspondingly bulky as a whole.
When it is desired to modify the location at which the PCB 1 and the FPC 4 are to be connected to each other, the location of the pin 3 or the threaded hole on the supporting member 2 must also be modified. Such modification makes the operation of modifying the positioning reference complex.
Further, as seen in FIG. 9, there may be a situation in which an actuator, such as an electric motor 6, and various electronic components are arranged immediately below the portions of the PCB 1 and the FPC 4 to be connected to each other and, as a result, the supporting member in the form of a casing is unavailable. In this case, it is impossible to provide the casing 7 with the pin 3 or the threaded hole and the operation of positioning the FPC 4 becomes difficult.